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A plane-sifter is a classifier in the mill for separating the grain components. Each plane-sifter contains several viewing compartments with sieve stacks. The separation process of sifting and stratification allows the ground material to be divided into components of different densities.
Plane-sifters were used at that time for sifting flour. These machines were invented by Karl Haggenmacher in Budapest in 1888 and replaced the hexagonal sifters.
https://de.wikipedia.org/wiki/Plansichter, accessed: 27. September 2019, 19:40 UTC